Hot wire thermal switch with calibration means for the contacts



June 27, 1967 J. HANCOCK HOT WIRE THERMAL SWITCH WITH CALIBRATION MEANS FOR THE CONTACTS 5 Sheets-Sheet 1 Filed Dec. 14, 1964 @2832 mmwxm INVENTOR. James L Hancock BY H15 ATTORNEY June 27, 1967 J. L HANCOCK 3,328,544

HOT WIRE THERMAL SWITCH WITH CALIBRATION MEANS FOR THE CONTACTS Filed Dec. 14, 1964 3 Sheets-Sheet 2 H15 ATTOR/VE Y June 27, 1967 J. HANCOCK 3,328,544

HOT WIRE THERMAL SWITCH WITH CALIBRATION MEANS FOR THE CONTACTS Filed Dec. 14, 1964 Sheets-Sheet 3 1- 8.0/6 AT 200,000 crass i g 1i 0.0% A7 200, 000 crass {3 E 2.5 m2 01750, 000 cycws E 1.0 -L\ Li K- k -070% A7 2'50, 000 (ZYC'LES 0.5

OPERATIONS w mama/v00 I I a 1 I a 5 L +0.0 AT .500, 000 cvcus -M A7 200, 000 was: 0.0 I 4 3 5.0 u; E 2.0

9 Q I l/ 2.7 0 A7300, 000 crass L 0.0 01504000 CYCLES 0.5

OPERATIONS 11v mousnuas v INVENTOR. 7. James 1. k'amc'ac/f 1?. 3 BY v H15 ATTORNEY United States Patent 3,328,544 HOT WIRE THERMAL SWITCH WITH CALIBRA- TIGN MEANS FOR THE CONTACTS James L. Hancock, Fairborn, Ohio, assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Filed Dec. 14, 1964, Ser. No. 418,102 4 Claims. (Cl. 200-139) This invention relates to hot wire relay and overload protector means, and, more particularly, to spacer means in combination therewith both for quick calibration and maintenance of reliable operation of movable contact means into variable positioning between complementary fixed contact means.

Calibration problems can involve costly loss of time and effort during manufacture of a switching device as well as difliculty for a customer having the device in use. A calibrating situation becomes even more challenging when multiple factors including positioning of contact means as well as tensioning of a hot wire portion or bimetallic member can be adjusted variously in attempting to attain an optimum condition.

An object of the present invention is to provide new and improved calibration spacer means engageable with at least a pair of fixed contact means to maintain predetermined distance therebetween regardless of movement of contact means complementary thereto.

Another object of this invention is to provide a hot wire relay and overload protector means having a pair of pivotally and flexibly mounted movable contact means with provision for minimum spacing therebetween though independently shiftable in response to current conditions in an adjustable hot wire portion which governs starting and running operation connections on a dynamoelectric machine means for example by way of the movable contact means in accordance with engagement of a pair of fixed contact means having insulating means in engagement with at least one fixed contact means to maintain predetermined positioning thereof subject only to adjustment of the hot wire portion during initial manufacture and subsequent operative use.

Another object of this invention is to provide a hot wire relay and overload protector means having a pair of pivotally and flexibly mounted movable contact means with provision for minimum spacing therebetween though independently shiftable in response to current conditions in an adjustable hot wire portion which governs starting and running operation connections on a dynamoelectric machine means for example by way of the movable contact means in accordance with engagement of a pair of fixed contact means each having'a projecting tongue means to one side of a cantilever mounting thereof laterally in adjustment with each other as well as with a third mounting reference projection, and a multi-slotted insulating plate portion that fits complementary with the reference projection as well as the pair of tongue means to establish and maintain predetermined positioning therebetween subject only to adjustment of the hot wire portion during initial manufacture and subsequent operative use.

A further object of this invention is to provide a spacer means of insulating material having a substantially parallelogram-shaped configuration including at least a pair of opposite ends as well as more than two slots transversely therein at least one of which is parallel to a reference slot to fit a projection of a mounting member of a hot wire relay and overload protector means, the remaining slots in the spacer means of insulating material having predetermined fit complementary to tongue means extending laterally from cantilever support portions of fixed contact means engaged by the movable contact means.

Another object of this invention is to provide a hot wire relay and overload protector means having a pair of pivotally and flexibly mounted movable contact means with provision for minimum spacing therebetween though independently shiftable in response to current conditions in an adjustable hot wire portion which governs starting and running operation connections on a dynamoelectric machine means for example by way of the movable contact means in accordance with engagement of a pair of fixed contact means carried by a base to which a cover portion is fitted having a pair of insulating lugs extending inwardly on the covering portion for predetermined engagement of at least one fixed contact base mounting portion and a further mounting portion carried also by the base.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein preferred embodiments of the present invention are clearly shown.

In the drawings:

FIGURE 1 is a plan view of a relay subassembly having features in accordance with the present invention.

FIGURE 2 is a side view of the relay subassembly of FIGURE 1.

FIGURE 3 is a plan view of insulation spacer means for calibration used in the relay subassembly of FIG- URES 1 and 2. I

FIGURE 4 is an end view of the spacer means of FIG- URE 3.

FIGURE 5 is a fragmentary exploded illustration of sides of a pair of fixed contact mounting means and a reference mounting projection provided in the subassembly of FIGURES 1 and 2.

FIGURE 6 is a partially sectioned end view of another embodiment of the present invention.

FIGURE 7 is a chart to show relay performance prior to the improvement in accordance with the present invention.

FIGURE 8 is a chart to show relay performance with features in accordance with the present invention.

A hot wire start and overload relay means is a switching device designed to provide starting control and overload protection on small single phase motors for exam ple. It can be used with split phase, condenser start and permanent condenser type motors and principally is found as a control device in connection with hermetically sealed refrigeration systems. Referring to views of FIGURES 1 and 2 of the drawings, such relay means includes a thermal responsive wire element 10 which controls operation of two single pole single throw switches 11 and 12. The thermal element 10 is connected in series'with motor circuitry of dynamoelectric machine generally indicated by numeral 14 in FIGURE 1 and including a rotor means 15 journaled in a well-known manner as well as a starting or phase winding portion '16 and main or running winding portion 17. A pair of cantilever contact support portions 18 and 19 for switches 12 and 11 respectively, which support respective fixed contacts 180 and 19c, can have a suitable rivet means or'fastening 181- and 191' respectively for mounting as to a base or platform portion 20. Such contacts supports 18 and 19 have a substantially cantilever or L-shaped configuration and free ends thereof in accordance with the present invention are provided with tongues or projections 18p and 19p integrally extending upwardly though having a width less than the cantilever supports 18 and 19 respectively. One pair Patented June 27, 1 967 ing device includes a minimum spacing member 21 between the switches 11 and 12 at free ends thereof to prevent closing of contacts 110 to contact 190 without having contacts 120 and 18c first operated. This minimum spacing member 21 is shown also in Patents 2,242,769-- Werner issued May 21, 1941, and 2,436,909--Werner issued Mar. 2, 1948, and both belonging to the assignee of the present invention. Reference can be made to these patent disclosures for further disclosure as to features of the switching device and operation including provision of a movable contact arm 22 hinged by a flat steel strip spring means 23 for carrying the movable contact structures 11 and 12. The stationary cantilever or L-shaped contact supports 18 and 19 are fixed as to one mounting end of each thereof and this fixing at such one end is also in a predetermined relationship laterally adjacent to a bracket or frame portion 24 secured to the platform or base 20. The bracket or frame portion 24 also has an upwardly extending tongue or projection portion 24p comparable to to the upwardly extending projections 18p and 19 provided integrally on the cantilever contact supports 18 and 19 respectively.

The thermal responsive hot wire or element is made of a nickel chromium alloy which has a high coefficient of linear expansion and good mechanical strength at elevated temperatures. It has relatively high specific resistance and the Wire temperature responds rapidly to the changes in current which it carries. Over the range of operating temperatures at which the Wire is worked, a change in wire length is obtained. This movement is transmitted and multiplied by the hinged arm portion 22 for obtaining still greater movement at the contact structure. The bracket 24 provides the attachment for the hinge spring means 23. Thus, one end of the hot wire or element 10 is secured to a spring secured end of the arm 22. An opposite end of the hot wire has a nut 25 engaging a threaded portion 26 for adjustment of the hot wire tension relative to a lug or transverse portion 27 or a bracket or support 28 also secured to the base or platform portion 20. In order to assure accurate and permanent wire calibration, maximum working stress thereof is held to within one third the elastic limit of the hot Wire portion 10.

Positioning of the fixed contact means 180 and 19c at cantilever supported or free ends of the members 18 and 19 respectively can vary during original manufacture sufficiently to cause difliculty in initial settings of the hot wire portion calibration by means of the nut 25 and threaded portion '26. Also the bracket 24 can vary slightly in positioning as to the fixed contact portions. Accordingly the upwardly extending projections 18p, 19p and 24p are provided therewith to receive a calibration member generally indicated by numeral 30 in views of FIG- URES 1 through 4 of the drawings. The calibration mem-.

ber 30 is in effect a predetermined spacer of insulating material having a substantially parallelogram-shaped configuration including at least a pair of opposite ends or edges 31 and 32 parallel to each other. Another pair of edges or sides 33 and 34 can also be parallel and a central body portion 35 between these edges 33 and 34 can be provided with a plurality of slots at least a pair of which designated by reference numerals 36 and 38 are also parallel to each other. An additional slot 39 is parallel to the opposite edges 31 and 32. The slots 38 and 39 have a predetermined angular relationship as to each other and fit complementary to the upwardly extending projections 18p and 19p of the cantilever contact supports or brackets 18 and 19 respectively. Positioning of the calibration member 30 onto the projections with a snug fit is accompanied by engagement of the third or additional slot 36 peripherally onto the upwardly extending projection 24p of the bracket 24. The bracket 24 as well as the cantilever fixed contact supports 18 and 19 with their upwardly extending projections are shown in perspective elevational positioning in a view of FIGURE 5. The calibration member 30 is a unitary piece of phenolic insulating material or other insulating plastic having stable dimensional characteristics regardless of temperature. The calibration member 30 can be press fitted into place on the predetermined upwardly extending projections and optionally can also be secured by a suitable adhesive such as epoxy resin means. The base or platform portion carrying the switching components as well as the calibration member can be housed in a box-like cover in which there is limited space and the press fit of the components to each other is generally sufficient to retain assembled relationship of the fixed contact cantilever supports or brackets 18 and 19 relative to the upwardly extending projection 24p of the bracket 24.

A cover portion of insulating material 40 is shown in FIGURE 6 of the drawings. The cover portion 40 as illustrated in FIGURE 6 is modified to provide another embodiment of the present invention for use in combination with the hot wire start and overload relay means described previously. The cover portion includes opposite sidewalls 41 as well as end walls 42 and a top 43 all of integral insulating material. Integral with the cover top portion 43 there are plural downwardly projecting lugs or insulating means designated by reference numerals 46, 48 and 49. These lugs 46, 48 and 49 have predetermined accurate positioning as to free ends of a bracket 124 cantilever switch support 118 and a further cantilever switch support 119 respectively carried by a base or platform portion 120. Also mounted on the base or platform portion is a support or bracket 128 having a transverse portion 127 to which hot wire element is fitted together with a nut 125 and threaded portion 126 similar structurally to features shown in views of FIGURES 1 and 2 of the drawings. A minimum spacing member 121 is provided between free ends of switches 111 and 112. Contacts 1110 and 1190 as well as contacts 1180 and 1120 are comparable to those described previously. The lugs 46, 48 and 49 are molded integrally with the insulating material of the cover portion 40 and the base or platform portion fits complementary thereto internally thereof such that the lugs engage the proper cantilever contact supports as well as the bracket 124. The nuts 25 and can be readily adjusted once the calibration member 30 or lugs establish predetermined positioning of the contacts laterally adjacent to each other as to a fixed reference provided by the bracket 124 or 24 engaged by the lug 46 or by the slotted portion 36 of the calibration member 30 respectively. Use of the calibration member 30 as well as the lugs integral with the cover portion can provide quick calibration for the hot Wire relay means contacts. Proper calibration assures proper operation and avoidance of contact damage or burning as well as faulty motor operation. It is to be understood that the lugs as well as the slots of the calibration member can be color coded. The calibration member 30 as well as the integrally molded lugs on the cover can result in a considerable reduction of cost and time. Also by using a calibration member 30 or the calibrating lugs integral with a cover the relay means continues to operate properly for a longer time be cause fatigue of metal support portions and bending or displacement thereof due to heat and usage cannot effect proper positioning of the predetermined contacts as to each other. It is to be understood that the slot arrangement of the calibration member 30 can be differed for various calibrations. Also it is to be noted that a solder dip is generally provided as to the hot wire adjustment nut 25 or 125 and the calibration member 30' assures maintenance of calibration of the contact portions once the hot wire per se is adjusted. The calibration member 30 also serves as a shield against movement of any of the free cantilever ends of the contact supports.

The use of calibration member 30 is more advantageous than the use of the lugs integral with the cover portion because then the contact portions can be provided with predetermined positioning in a subassembly as represented in views of FIGURES 1 and 2 of the drawings.

Use of the calibration member 30 assures proper dimensional relationships for proper calibration since then all the upwardly extending projecting tongues or points are within tolerances by use of a fixed structure.

Successful calibration can be achieved with the lugs as well as the calibration member 30 and the charts of FIG- URES 7 and 8 of the drawings illustrate discrepancy in calibration of relay means without the calibration feature in FIGURE 7 and the considerable improvement in the repeated cycling of relay means using the calibration feature is shown by FIGURE 8 of the drawings. Maintenance of the proper calibration assures operation of the relay means within proper range of starting and running conditions of current supplied to the motor or dynamoelectric machine. A substantial reduction in cost is achieved not only as to the time for calibrating but also the cost of tooling. Features of the present invention permit presetting calibration of the contact make and break operation requiring only adjustment of a single Wire tension nut. The hot wire relay and overload protector means modified to include the calibration member 30 slotted in three locations of predetermined distance and angulation therebetween to meet telescopically with the upwardly extending projections of the pair of spring contact engageable fixed contact supports and the more rigid bracket 24 as a reference point can assure proper operation.

This operation briefly can be summarized as follows:

When the motor is not energized, both sets of contacts are closed. When the motor is energized, line current is carried through the thermal element 110 or 10 which expands and moves a hinged arm such as 22 to a position at which the starting contacts 120 and 180 open thereby cutting the starting winding out of the circuit. This operation takes place in from one to five seconds. Shorter starting periods are desirable on motors which accelerate rapidly and longer periods are required on heavier applications. After the motor is started, the current decreases to a value which under all normal loads is suflicient to hold the starting contacts open and not high enough to cause the thermal element to expand a suflicient amount to open the main winding contacts. When the line current is removed, the thermal element will cool and contract and reset the starting contacts after a few seconds.

If an attempt is made to restart the motor before the starting contacts have reset, the main winding locked rotor current is high enough to trip the relay overload contacts 110 and 19c in a few seconds and open the line circuit. After a period of substantially one quarter to one minute, the thermal relay means will automatically reset both starting and overload contacts and restart the motor. This automatic operation takes care of short period power failures which will allow the motor to stall but are not long enough to permit the starting contacts to reset. Heavy motor overloads will cause the same sequence of operations to take place. The overload contacts 11c and 190 (also 111c and 1190) will trip and open the line circuit, thereby permitting the motor and relay to cool subject to resetting of both sets of contacts automatically. If the overload is due to some temporary condition which is relieved after a short period of time, the motor will continue to operate in a well known manner. If, however, the overload is permanent, such as a tight hearing which stalls the motor, the relay will automatically cycle at a rate which will hold the motor winding temperature within safe limits and prevent motor burnout.

The calibration member 30 ties down specific distances from the frame or bracket 24 to each of the stationary post or contact supports 18 and 19. Variation in alignment between such stationary post or contact supports is avoided regardless of the riveting operation as to the platform or base portion 20. Thus drift of settings is minimized and the improved performance characteristics illustrated by FIGURE 8 of the drawings can be gained as an improvement over the characteristics of FIGURE 7 for previous relay means. It is to be noted that in the chart of FIGURE 7, most deviation from the proper setting occurs at one hundred thousand cycles of operation for relay means tested without the calibration feature in accordance with the present invention. In the chart of FIGURE 8, it can be seen that nearly twice as many cycles or substantially one hundred eighty thousand cycles can be run before any appreciable deviation in contact operation and setting occurs. Thus, factors of wear and possible contact deterioration being equal, the calibration features in accordance with the present invention can provide an appreciable and decided advantage over the structures previously provided.

While the embodiments of the present invention herein disclosed constitute preferred forms, it is to be understood that other forms might be adopted.

What is claimed is as follows:

-1. A hot wire relay and over-load protector unit comprising, a base portion of insulating material, a plurality of cantilever supported fixed contacts secured to said base portion, a bracket member carrying a plurality of pivotally and flexibly mounted movable contacts each corresponding to a respective one of said fixed contacts, a hot wire portion adjustable at one end as carried by said bracket portion and secured at the opposite end thereof to said pivotally and flexibly mounted movable contacts, a minimum spacing member fitted between said movable contacts, a cover portion complementary to said base portion and a lug member corresponding to each one of said fixed contacts carried by said cover portion engageable with the corresponding said fixed contact for adjusting the engaged said corresponding fixed contact in a direction relative to another one of said fixed contacts to accurately position said fixed contacts in a predetermined spaced relationship by the operation of placing said cover member upon said base portion.

2. A hot wire relay and over-load protector unit as defined in claim 1 wherein said lug members are an integral part of said cover portion, said cover portion and said base portion being of insulating material.

3. A hot wire relay and overload protector unit comprising, a base portion of insulating material, a plurality of cantilever supported fixed contacts each having an upwardly extending projection secured to said base portion, a bracket member having an upwardly extending projection carrying a plurality of pivotally and flexibly mounted movable contacts each corresponding to a respective one of said fixed contacts, a hot wire portion adjustable at one end as carried by said bracket portion and secured at the opposite end thereof to said pivotally and flexibly mounted movable contacts, a minimum spacing member fitted between said movable contacts and a calibration member of insulating material having slots therein in predetermined positions for accommodating said upwardly extending projections of said bracket member and said stationary contact members whereby said stationary contact members are calibrated in reference to said bracket member.

4. A hot wire relay and overload protector unit as defined in claim 3 wherein said calibration member is of a parallelogram shaped configuration including at least one pair of parallel slots therein for complementary fit into engagement with said upwardly extending projection on said bracket member and said upwardly extending projection of one of said figxed contact members.

References Cited UNITED STATES PATENTS 2,43 6,909 3/ 1948 Werner 200-113 2,860,209 11/1958 Hadley 200-113 3,098,905 7/ 1963 Anderson 200166 X BERNARD A. GILHEANY, Primary Examiner.

T. MACBLAIN, H. A. LEWITTER, Assistant Examiners. 

3. A HOT WIRE RELAY AND OVERLOAD PROTECTOR UNIT COMPRISING, A BASE PORTION OF INSULATING MATERIAL, A PLURALITY OF CANTILEVER SUPPORTED FIXED CONTACTS EACH HAVING AN UPWARDLY EXTENDING PROJECTION SECURED TO SAID BASE PORTION, A BRACKET MEMBER HAVING AN UPWARDLY EXTENDING PROJECTION CARRYING A PLURALITY OF PIVOTALLY AND FLEXIBLY MOUNTED MOVABLE CONTACTS EACH CORRESPONDING TO A RESPECTIVE ONE OF SAID FIXED CONTACTS, A HOT WIRE PORTION ADJUSTABLE AT ONE END AS CARRIED BY SAID BRACKET PORTION AND SECURED AT THE OPPOSITE END THEREOF TO SAID PIVOTALLY AND FLEXIBLY MOUNTED MOVABLE CONTACTS, A MINIMUM SPACING MEMBER FITTED BETWEEN SAID MOVABLE CONTACTS AND A CALIBRATION MEMBER OF INSULATING MATERIAL HAVING SLOTS THEREIN IN PREDETERMINED POSITIONS FOR ACCOMMODATING SAID UPWARDLY EXTENDING PROJECTIONS OF SAID BRACKET MEMBER AND SAID STATIONARY CONTACT MEMBERS WHEREBY SAID STATIONARY CONTACT MEMBERS ARE CALIBRATED IN REFERENCE TO SAID BRACKET MEMBER. 